Aluminum Hybrid Reinforcement Technology is a response to the dynamic ever-increasing service requirement of industries such as transportation, aerospace, automobile, and marine, due to its attractive properties like high ductility, highly conductivity, light weight, and high strength to weight ratio. In this evolution, an attempt has been made to investigate the wear rate of Al6061 hybrid metal matrix composite reinforced with the hard ceramic alumina (4, 8, and 12 wt.% of Al2O3) and soft solid lubricant of molybdenum disulphide (2, 4, and 6 wt.% of MoS2) is fabricated by using stir casting method. The unlubricated pins on disc wear tests were conducted to examine the wear behaviour of Al6061/12 wt.% of Al2O3/MoS2 composites. The sliding wear tests were carried out at various loads of 15, 30, and 45 N, sliding velocity (1.25, 2.50, and 3.25 m/sec), and different MoS2 wt.% (2, 4, and 6 wt.%). In addition, the CNC turning experiments were conducted on Al6061/12 wt.% Al2O3/6 wt.% MoS2 using CNMG 120408 uncoated carbide cutting tool under cutting of 100, 150, and 200 m/min, feed of 0.1, 0.2, and 0.3 mm/rev, and depth of cut of 1, 1.5, and 2 mm.
Aluminum hybrid matrix composites have become better substitutes for the conventional aluminum alloys because of their characters like improved strength to weight ratio, energy saving, and better wear resistance [
Anilkumar et al. [
Singh et al. [
Sharanabasappa and Motgi [
Wang and Yan [
However many researchers have carried out the mechanical and wear properties and machining characteristics of aluminum metal matrix composites with SiC and Al2O3 as reinforcing materials. In the case of hybrid Al6061/Al2O3/MoS2 composites, limited literature is available, encompassing various aspects such as mechanical properties and wear behaviour and conducting the machining study of the composites. Aluminum based Al2O3 composite material has properties such as low weight, heat resistant, wear resistant, and low cost. These are found in various engineering applications such as cylinder block liners, vehicle drive shafts, automotive pistons, and bicycle frames. These materials are known as difficult to machine materials, because of the hardness and abrasive nature of reinforcement element like alumina particle [
The stir casting method is simple and the most economical way of fabricating particulate reinforced composites. In this technique, to accomplish the optimum properties of the hybrid composites, the distribution of the reinforced particles in the base material should be homogeneous and the wettability among the olden materials and particulates ought to be optimized. The moisture level in the cast composite must be reduced and the element reactions among the particles and the base material have to be avoided. The whirlpool method is one of the enhanced recognized tactics used to build a high quality allocation of the reinforced material in the base matrix. In this method, the base material is melted followed by a forceful stirring by automatic agitator to form a whirlpool at the face of dissolve, and the particle is subsequently introduced at the region of the vortex.
The chemical composition of Al6061 alloy is given in Table
Chemical composition of Al6061 alloy.
Si | Fe | Cu | Mn | Mg | Cr | Zn | Ti | Al |
0.65 | 0.7 | 0.25 | 0.15 | 0.8 | 0.07 | 0.25 | 0.15 | Remaining |
The hardness tests were carried out according to ASTM E10-07 standards using Brinell hardness testing machine with a 10 mm ball indenter and 500 kg load for 30 sec. The test was carried out at atmospheric temperature (30°C) and the measurement of hardness was taken at three different locations on each sample to obtain an average value of hardness. As per the ASTM E08-8 standard, the tensile strength was evaluated on the cylindrical rod of casted composites. The 1200 grit grindings silicon carbide paper was used to polish the test specimens in order to decrease the machining scratches and the effects of surface defects on the sample. The universal testing machine was loaded with 10 KN; load cell was used to conduct the tensile test. The affecting factors and levels selected for mechanical behaviour Al6061/Al2O3/MoS2 are given in Table
Affecting factors and levels selected for tensile strength Al6061/Al2O3/MoS2.
Factors/levels | 1 | 2 | 3 |
| 4 | 8 | 12 |
| 2 | 4 | 6 |
Dry sliding wear behaviour of Al6061/12 wt.% Al2O3/MoS2 hybrid composites is studied in pin on disc test apparatus. Pin specimens of 6 mm diameter and 15 mm height, for wear test, were prepared from the above composites and the composites were machined and polished. The test was conducted with various loads of 15 N, 30 N, and 45 N at a sliding speed of 125, 2.50, and 3.25 m/s and 2, 4, and 6 MoS2 wt.%. It was conducted at room temperature (30°C) and relative humidity of 60–65%. The affecting factors and levels selected for Tribology Al6061/12 wt.% Al2O3/MoS2 are given in Table
Affecting factors and levels selected for Tribology Al6061/12 wt.% Al2O3/MoS2.
Factors/levels | 1 | 2 | 3 |
| 15 | 30 | 45 |
| 1.25 | 2.50 | 3.25 |
| 2 | 4 | 6 |
The work material used for the present investigation is Al6061/12 wt.% Al2O3/6 wt.% MoS2 and diameter of the material is 20 mm and machined length is 60 mm for all trials. The experiments were conducted on Fanuc CNC lathe and CNMG 120408; uncoated carbide cutting tool is used as the insert for all machining operations. The affecting factors and levels selected for turning properties Al6061/12 wt.% Al2O3/6 wt.% MoS2 are given in Table
Affecting factors and levels selected for turning properties Al6061/12 wt.% Al2O3/6 wt.% MoS2.
Factors/levels | 1 | 2 | 3 |
| 100 | 150 | 200 |
| 0.1 | 0.2 | 0.3 |
| 1 | 1.5 | 2 |
The tensile strength and hardness of the Al6061/4, 8, and 12 wt.% Al2O3/2, 4 wt.% MoS2 hybrid composite are shown in Figures
(a) Mechanical behaviour of Al6061/2 wt.% of MoS2/4 : 8 : 12 wt.% of Al2O3. (b) Mechanical behaviour of Al6061/4 wt.% of MoS2/4 : 8 : 12 wt.% of Al2O3. (c) Mechanical behaviour of Al6061/6 wt.% of MoS2/4 : 8 : 12 wt.% of Al2O3.
The measured values of tensile strength and BHN for Al6061/Al2O3/MoS2 under different wt.% and corresponding signal to noise ratio for all experimental runs are given in Table
Experimental result for tensile strength of Al6061/Al2O3/MoS2.
Trial | | | Al2O3 (wt.%) | MoS2 (wt.%) | TS (N/mm2) | S/N ratio | BHN | S/N ratio |
---|---|---|---|---|---|---|---|---|
1 | 1 | 1 | 4 | 2 | 201.5 | 46.0855 | 94.56 | 33.2713 |
2 | 1 | 2 | 4 | 4 | 219.7 | 46.8366 | 96.78 | 33.4117 |
3 | 1 | 3 | 4 | 6 | 207.4 | 46.3362 | 97.37 | 33.3184 |
4 | 2 | 1 | 8 | 2 | 221.4 | 46.9036 | 98.67 | 33.4241 |
5 | 2 | 2 | 8 | 4 | 237.2 | 47.5023 | 104.76 | 33.5343 |
6 | 2 | 3 | 8 | 6 | 227.8 | 47.1511 | 103.32 | 33.4698 |
7 | 3 | 1 | 12 | 2 | 243.4 | 47.7264 | 106.23 | 33.5752 |
8 | 3 | 2 | 12 | 4 | 259.5 | 48.2827 | 107.56 | 33.6758 |
9 | 3 | 3 | 12 | 6 | 251.3 | 48.0038 | 104.57 | 33.6255 |
Taguchi analysis: TS & BHN versus
Level | TS | BHN | ||
---|---|---|---|---|
| | | | |
1 | 46.42 | | 33.33 | 33.42 |
2 | 47.19 | 47.54 | 33.48 | |
3 | | 47.16 | | 33.47 |
Delta | 1.58 | 0.64 | 0.29 | 0.12 |
Rank | 1 | 2 | 1 | 2 |
Analysis of variance for TS & BHN of Al6061/Al2O3/MoS2.
Source | DF | TS | BHN | ||||||
---|---|---|---|---|---|---|---|---|---|
Seq SS | Adj MS | | | Seq SS | Adj MS | | | ||
| 2 | 2634.78 | 1317.39 | 1092.26 | 0.000 | 3.7691 | 1.8845 | 480.69 | 0.000 |
| 2 | 423.56 | 211.78 | 175.59 | 0.000 | 0.6125 | 0.3063 | 78.12 | 0.001 |
Error | 4 | 4.82 | 1.21 | 0.0157 | 0.0039 | ||||
Total | 8 | 3063.17 | 4.3973 | ||||||
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The variation of wear rate for Al6061/12 wt.% Al2O3/MoS2 hybrid composite with respect to different sliding velocity and applied load is shown in Figures
(a) Wear rate of Al6061/12 wt.% Al2O3/MoS2 during sliding velocity of 1.25 m/sec. (b) Wear rate of Al6061/12 wt.% Al2O3/MoS2 during sliding velocity of 2.50 m/sec. (c) Wear rate of Al6061/12 wt.% Al2O3/MoS2 during sliding velocity of 3.25 m/sec.
The coefficient of friction for Al061/12 wt.% Al2O3/MoS2 hybrid composites under varying load and sliding velocity is shown in Figures
(a) Coefficient of friction of Al6061/12 wt.% Al2O3/MoS2 during sliding velocity of 1.25 m/sec. (b) Coefficient of friction of Al6061/12 wt.% Al2O3/MoS2 during sliding velocity of 2.50 m/sec. (c) Coefficient of friction of Al6061/12 wt.% Al2O3/MoS2 during sliding velocity of 3.25 m/sec.
The wear surface of the Al6061/12 wt.% Al2O3/6 wt.% MoS2 under sliding velocity of 2.50 m/sec is given in Figures
(a) Wear surface of Al6061/12 wt.% Al2O3/6 wt.% MoS2 tested at 15 N load. (b) Wear surface of Al6061/12 wt.% Al2O3/6 wt.% MoS2 tested at 45 N load.
The experimental values of wear rate and coefficient of friction for Al6061/12 wt.% Al2O3/MoS2 under different parameters and corresponding signal to noise ratio for all experimental runs are given in Table
Experimental results for Al6061/12 wt.% Al2O3/MoS2 of wear study.
Trial | | | | Load (N) | Sliding velocity (m/s) | wt.% of MoS2 (wt.%) | Wear rate (mm3/min) × 10−3 | S/N | Coefficient of friction | S/N |
---|---|---|---|---|---|---|---|---|---|---|
1 | 1 | 1 | 1 | 15 | 1.25 | 2 | 1.346 | −2.580 | 0.487 | 6.249 |
2 | 1 | 2 | 2 | 15 | 2.50 | 4 | 1.250 | −1.938 | 0.455 | 6.839 |
3 | 1 | 3 | 3 | 15 | 3.25 | 6 | 0.966 | 0.300 | 0.423 | 7.473 |
4 | 2 | 1 | 2 | 30 | 1.25 | 4 | 2.344 | −7.399 | 0.523 | 5.629 |
5 | 2 | 2 | 3 | 30 | 2.50 | 6 | 2.576 | −8.218 | 0.496 | 6.090 |
6 | 2 | 3 | 1 | 30 | 3.25 | 2 | 2.133 | −6.579 | 0.537 | 5.400 |
7 | 3 | 1 | 3 | 45 | 1.25 | 6 | 2.756 | −8.805 | 0.568 | 4.913 |
8 | 3 | 2 | 1 | 45 | 2.50 | 2 | 3.813 | −11.625 | 0.603 | 4.393 |
9 | 3 | 3 | 2 | 45 | 3.25 | 4 | 3.245 | −10.224 | 0.579 | 4.746 |
Taguchi analysis: wear rate and coefficient of friction versus
Level | Wear rate | Coefficient of friction | ||||
---|---|---|---|---|---|---|
| | | | | | |
1 | − | −6.262 | −6.929 | | 5.597 | 5.348 |
2 | −7.399 | −7.261 | −6.521 | 5.707 | 5.775 | 5.739 |
3 | −10.218 | − | − | 4.684 | | |
Delta | 8.812 | 1.760 | 1.354 | 2.170 | 0.276 | 0.811 |
Rank | 1 | 2 | 3 | 1 | 3 | 2 |
Analysis of variance for wear rate of Al6061/12 wt.% Al2O3/MoS2.
Wear rate | Coefficient of friction | ||||||||
---|---|---|---|---|---|---|---|---|---|
Source | | Seq SS | Adj MS | | | Seq SS | Adj MS | | |
| 2 | 6.5442 | 3.2721 | | | 0.0247047 | 0.0123523 | | |
| 2 | 0.3456 | 0.1728 | 1.53 | 0.395 | 0.0002580 | 0.0001290 | 7.90 | 0.112 |
| 2 | 0.1651 | 0.0826 | 0.73 | 0.577 | 0.0032667 | 0.0016333 | 100.00 | 0.010 |
Error | 2 | 0.2252 | 0.1126 | 0.0000327 | 0.0000327 | ||||
Total | 8 | 7.2801 | 0.0282620 | ||||||
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The experimental results of arithmetic mean value for turning Al6061/12 wt.% Al2O3/6 wt.% MoS2 under different cutting conditions and corresponding signal to noise ratio for all experimental runs are given in Table
Experimental result of surface roughness for Al6061/12 wt.% Al2O3/6 wt.% MoS2.
Trial | | | | | | | Ra ( | S/N ratio |
---|---|---|---|---|---|---|---|---|
1 | 1 | 1 | 1 | 100 | 0.1 | 1 | 2.21 | −6.887 |
2 | 1 | 2 | 2 | 100 | 0.2 | 1.5 | 2.35 | −7.421 |
3 | 1 | 3 | 3 | 100 | 0.3 | 2 | 3.56 | −11.029 |
4 | 2 | 1 | 2 | 150 | 0.1 | 1.5 | 2.48 | −7.889 |
5 | 2 | 2 | 3 | 150 | 0.2 | 2 | 2.65 | −8.464 |
6 | 2 | 3 | 1 | 150 | 0.3 | 1 | 3.62 | −11.174 |
7 | 3 | 1 | 3 | 200 | 0.1 | 2 | 2.88 | −9.187 |
8 | 3 | 2 | 1 | 200 | 0.2 | 1 | 3.02 | −9.600 |
9 | 3 | 3 | 2 | 200 | 0.3 | 1.5 | 3.87 | −11.754 |
Taguchi analysis: Ra versus
Level | | | |
---|---|---|---|
1 | − | − | −9.221 |
2 | −9.176 | −8.495 | − |
3 | −10.181 | −11.319 | −9.561 |
Delta | 1.735 | 3.331 | 0.539 |
Rank | 2 | 1 | 3 |
Analysis of variance for Ra of Al6061/12 wt.% Al2O3/6 wt.% MoS2.
Source | DF | Seq SS | Adj SS | Adj MS | | |
---|---|---|---|---|---|---|
| 2 | 0.46220 | 0.46220 | 0.23110 | 24.85 | 0.039 |
| 2 | 2.38820 | 2.38820 | 1.19410 | | |
| 2 | 0.02580 | 0.02580 | 0.01290 | 1.39 | 0.419 |
Error | 2 | 0.01860 | 0.01860 | 0.00930 | ||
Total | 8 | 2.89480 | ||||
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In the present investigation, the Al6061/Al2O3/MoS2 hybrid composite is successfully fabricated using stir casting process. The mechanical behaviour, tribological behaviour, and machinability behaviour are evaluated. The obtained results can be summarized as follows: Mechanical properties of hybrid composites increase with an increase in weight fraction of alumina particles. An increase in weight fraction of molybdenum disulphide reinforcement decreases the mechanical properties like tensile strength and BHN. The optimum parameter for maximization of tensile strength is obtained at 12 wt.% of Al2O3 and 2 wt.% of MoS2 and the maximum BHN is obtained at 12 wt.% of Al2O3 and 4 wt.% of MoS2. The incorporation of Al2O3 reinforcement to Al6061 increases the wear resistance of the composites. The addition of MoS2 reinforcement in Al6061/Al2O3 composites as a hybrid reinforcement further increases the wear and friction resistance of the composite. This is attributed to the stable and MoS2 rich mechanically mixed layer, which prevents metal to metal contact and reduces the wear of the composite. The unstable mechanically mixed layer in the absence of the lubricant phase leads to lower wear resistance in Al6061/Al2O3/MoS2 hybrid composite. The optimum parameter for minimization wear rate and coefficient of friction are obtained at 15 N of load, 3.25 m/sec of sliding velocity, and 6 wt.% of MoS2. The optimum parameter for minimization surface roughness is obtained at 100 m/min of cutting speed, 0.1 mm/rev of feed, and 1.5 mm of depth of cut for CNC turning Al6061/12 wt.% Al2O3/6 wt.% MoS2 hybrid composite.
The authors declare that they have no competing interests.